1. Scope of the Invention
The present invention relates generally to poly(arylene ether) compositions and methods of manufacture thereof, and more specifically to poly(arylene ether) polymers that form low dielectric constant, low moisture absorbing and high glass transition temperature dielectric films for microelectronic devices, and methods of manufacture thereof.
2. Related Art
Advances in the semiconductor industry are characterized by the introduction of new generations of integrated circuits (IC's) having higher performance and greater functionality than that of the previous generation. These advances are often the result of reducing the size of the IC devices. However, as device geometries approach and then go beyond dimensions as small as 0.25 micron (.mu.m), the dielectric constant of an insulating material used between conductive paths, for example silicon oxide (SiO.sub.2), becomes an increasingly significant factor in device performance. As the distance between adjacent conductive paths becomes smaller, the resulting capacitance, a function of the dielectric of the insulating material divided by the distance between conductive paths, increases. As a result, capacitive coupling between adjacent conductive paths is increased. The increased capacitance additionally results in increased power consumption for the IC and an increased RC time constant. The latter resulting in reduced signal propagation speed. In addition, the increased capacitance can result in cross talk between adjacent paths, or layers of paths, thus lowering the signal to noise ratio.
Organic insulating materials can provide films having dielectric constants in the range of approximately 2.0-3.0, significantly lower than the 3.9 of a SiO.sub.2 film. Thus reduced capacitance is provided and the aforementioned problems alleviated. However, any organic material must meet other criteria in addition to a low dielectric constant before it can be used to replace the commonly employed SiO.sub.2. For example, the material should have a glass transition temperature (Tg) of at least 350 degrees Celsius (.degree. C.), good thermal stability to and above the Tg, a low moisture absorption rate and good retention of the storage modulus above the material's Tg.
One attempt at such an organic material and an IC application that uses the material are the subjects of European Patent Application EP 0 755 957 A1, "NONHALOGENATED POLY(ARYLENE ETHERS)," ('957 application), and a related U.S. Pat. No. 5,658,994, "NONFUNCTIONALIZED POLY(ARYLENE ETHER) DIELECTRICS," ('994 patent), both by Burgoyne, Jr., et al. The '994 patent is directed to "a dielectric material provided on a microelectronic device, wherein the dielectric material contains a poly(arylene ether) polymer" (column 3, lines 25-27). The '957 application, is directed to "the field of poly(arylene ethers) which do not contain any metal-reactive groups in the polymer, such as activated fluorine substituents." (page 2, lines 1-2). The poly(arylene ethers) of the '957 application appear to be the dielectric material of the '994 patent. However, the poly(arylene ethers) of Burgoyne Jr., et. al., among other things, have glass transition temperatures below 300.degree. C. (Table 3 in the '957 application) which can be problematic during commonly employed Chemical Vapor Depositions of tungsten at 450.degree. C. In addition, Burgoyne, Jr., et al. suggests the use of adhesion promoters with the poly(arylene ethers) of the '994 patent (see column 9, lines 41-50). However, the use of adhesion promoters, such as the hexamethyldisilazane suggested by Burgoyne, Jr., et al. typically require an additional process step and often result in an increase in the amount of outgassing from the polymer film hence, lower thermal stability.
Another example of an aromatic hydrocarbon polymer for use a dielectric material has been announced by the Dow Chemical Company under the tradename SILK. The polymer contains no silicon or fluorine. This material was described to possess high thermal stability and Tg and a dielectric constant of 2.65. An adhesion promotor is typically required with this material, as are long cure times and special process equipment.
Yet another example of an organic material for use as a dielectric material is a family of fluorinated poly(arylene ethers) having dielectric constants in the range of 2.36-2.65. These fluorinated poly(arylene ethers) are described in U.S. patent application, Ser. No. 08/665,189 ('189 application) filed Jun. 14, 1996. The '189 application is entitled "IMPROVED POLY(ARYLENE ETHER) COMPOSITIONS AND THE METHOD FOR THEIR MANUFACTURE" and assigned to the assignee of the present application. However, while the polymers of the '189 application have acceptably low dielectric constants and high Tg, adhesion of these polymers to common semiconductor surfaces, without the use of adhesion promoters, is at times problematic.
Thus it would be desirable to manufacture and use an organic dielectric material having a Tg value above 350.degree. C. and preferably above 400.degree. C. It would also be desirable for the organic dielectrics manufactured to have good adhesion to a variety of common semiconductor surfaces without the use of adhesion promoters. In addition, it would be desirable for the organic dielectrics to have good gap-filling qualities and thus completely fill spaces between conductive traces of 0.25 .mu.m or less. Additionally, it would be desirable to manufacture and use an organic dielectric material having good dimensional stability above the dielectric material's Tg, e.g. storage modulus. It would further be desirable for the organic dielectrics to have good thermal stability, as evidenced by little or no outgassing and low moisture absorptivity up to and beyond the Tg. For use as an interlayer dielectric in a multilevel metal construct, it would be desirable for the organic film to additionally be stable toward a variety of common etching and planarization, i.e., CMP (chemical mechanical polishing) processes. It would further be desirable for the organic dielectrics to be easily processed in high yield to substrates, for example using standard spin-bake-cure processing techniques, using the lowest possible cure temperatures and short cure times, thus insuring their cost effectiveness. Finally, it would be desirable for the organic dielectrics manufactured to also be applicable to use in other microelectronic devices in addition to ICs, for example printed circuit boards (PCBs), multichip modules (MCM's) and the like.